Electric discharge tube



Oct. 25, 1932. c. 1.. DAVIS ELECTRIC DISCHARGE TUBE Filed April 1, 1929 51 quency characteristics Patented Oct. 25, 1932 COLUMBIA, ASSIGNOR A CORPORATION OF DELAWARE TO WIRED ELECTRIC DISCHARGE 'IUIBE' Application filed April 1, 1929. Serial My invention relates to the frequency signaling systems.

11 object of my invention is to provide means for automatically controlling the freof a high frequency control of high thermionic tube.

Another object of my invention is to provide means for preventing variations of temperature from afiecting the frequency char- IQ' acteristics of a high frequency signaling quency signaling system.

A further object of my invention is to pro vide a frequency controlling unit adapted to counteract changes in frequency caused by changes in temperature.

, Figure 1 is a diagrammatic circuit arrange ment' explaining the principles of my invention in which the effective inductance in a circuit is controlled in accordance with changes in temperature; Fig. 2 shows a diagrammaticcircuit arrangement in which the effective capacity in a circuit may be controlled in accordance with changes in temperature; 3 is an elementary view showing one method I employ in mounting the condenser system by means of a thermoexpansive element by which the spacial relation of armatures of condenser in an electrical circuit may be varied in accordance with changes in temperature; Fig. 4 illustrates a modified arrangement of thermoexpansive element arranged to control the capacity of a condenser system in accordance with temperature changes; and Fig. 5 shows the preferred em bodiment of my invention in which a compensating condenser is mounted within the evacuated vessel which contains the tube electrodes, the compensating condenser being variable in accordance with changes in temperature within the tube.

As is well known to those skilled in the art the frequency characteristics of a high fresystem are difficult to control. Mechanically vibratile elements have been employed and divers arrangements for maintaining the frequencycharacteristics of an oscillatory circuit constant have been introduced.

The temperature of an inductance or a conciated. Conversely frequency characteristics of the circuit of which they are a part. A metallic inductance will expand with increases of tempera.

ture and contract with decreases of temperature. The expansion of the metal increases the value of inductance and the contraction the metal reduces the value of inductance. The expansion, therefore, decreases the frequency characteristics of the circuit of "which. it is a part and the contraction increases the frequency characteristics.

In like manner the capacity of a condenser is largely determined by the area of the metal plates which increase in area with an increase of temperature and decrease in area with a decrease of temperature. The increase in area increases the capacity and consequently decreases the frequency characteristics of the circuit with which it is assothe decrease in area decreases the capacity and consequently increases the frequency characteristics of the circuit with which it is associated. The increase or decrease of temperature therefore causes changes in the frequency characteristics of the elements employed in high frequency signaling systems and the improvements in frequency stabilization of my invention overcome this unstable condition.

Fig. 1 shows an inductance 1 which comprises metal wire, strip or tubing the fre quency characteristics of which are modified in accordance with the value of capacity of condenser 2. An auxiliary coil 8 is provided having a plurality of connections from different portions thereof connected to a plurality of contact members. Contact members 4 are lengths of wire sealed through the neck of a thermometer 5. The mercury or other conducting material'in thermometer 5 rises with an increase of temperature thereby short-circuiting different sections of coil 3.

his causes a reduction of the inductance in the circuit. The same variations of temperature which causes the mercury to rise also causes the metal of coil 1 to expand. The expansion of coil 1 decreases the frequency characteristics of the circuit, however the change in the frequency characteristics of tationary plate -10. Stationary capacity of condenser 2 may also change with the temperature and the change in the inductance of coil 3 counteracts the change in capacity. a i

It is possible to control the value of capacity instead of controlling the value of inductance as shown in Fig. 1. Fig. 2 shows such an arrangement where the metastatic type of thermometer is employed. Similar reference characters have been used in all of the figures to indicate corresponding parts. Contact members 4 are connected to a plurality of condenser elements 6, 7 which are across the condenser 2. Condensers 7, nearest the bottom of thermometer 5 may be of a value different than condensers 6, nearest the top of the thermometer. An increase of temperature thereby connects different con densers in the circuits. This shows how it is possible to decrease the frequency characteristics of a circuit in proportion to an increase of temperature. This would be especially desirable where different circuits are subjected to different operational temperatures and whereby an increase in temperature of one circuit causing a decrease in frequency would necessit te decreasing the frequency characteristics if a circuit associated therewith to maintain resonance.

Fig. 3 shows the preferred form of the means for frequency stabilization of my invention. Coil 1 is associated with a bimetallic. member 8. Me ber 8 comprises dissimilar metals such as iron and brass having different coefficients of expansion. movable condenser plate 9 is carried by member 8 and is movable in a plane adjacent to plate 10 is electrically connected to the end of coil 1 opposite the end connected to plate 9. It is not necessary nected across coil 1 in its entirety, one or more turns of the coil maybe sufficient. Changes in the temperature to which member 8 is subjected cause member Sto swerve in a given direction increasing or decreasing the capacitive relation between plates 9 and 10,

depending upon whether the changes are devariations of coil 1 and the creasing or increasing temperatures.

Fig. 4 shows an arrangement which is more sensitive than the arrangement shown in the foregoing figures. Bi-metallic member 8a is here shown as a spiral having one end positioned and the movable end carrying a plate 9. Plate 9 is in capacitive relation to inductance'l which capacitive relation is l varied in accordance with changes in the temperature. The relation in each instance is such as to counteract the variation in the frequency characteristics of coil 1 or condenser 2. Since both coil 1 and condenser 2 are subject to variations in frequency characteristics with variations of temperature the variations of condenser 2 contribute to the ordinary change that plates 9 and 10 be conby variations in the frequencycharacteristics of the elements or in other words by the variation in the physical dimensions of relative positions of the elements in the thermionic tube. It is apparent that the internal temperature of thermionic tubes varies between somewhat wide limits caused by many factors within the tube as well as the external circuit characteristics, the load supplied and the source of energizing potential supplied the elements of the tube. I have noticed that changes in the load circuit "cause considerable change in the frequency of the generated energy. This is due almost entirely to changes in the current through the tube or the internal circuit. Changes in such current cause material changes in the physical dimensions of the anode and control electrodes. Changes in the power supplied the electrodes causea change of internal'tem perature of the tube as the electronic current isthus affected and this in turn causes a change in the physical dimensions of the elements within the tube. Attempts have been made to control the frequency characteristics of the external circuit by means of mechanically vibratile elements, and while such efforts have been fairly successful, the at-. tack. upon the problem has been very indirect. I have found that greater accuracy in frequency control is secured by providing frequency compensation arrangements within the thermionic tube itself or so closely adjacent thereto as to be influenced only by the temperature of the tube. I I

Fig. 5 shows the frequency stabilizing means of my invention applied to a thermionic tube 11. Thermionic tube 11 has an anode 12, cathode 13 and one or more contro electrodes (not shown). Bi-metallic member 8 is carried by anode 12 or in any conven- .ient manner associated with the tube whereby it will be actuated by the changes in the.-

ditions.

Condenser plates9 arid 10 are here shown temperature of the tube under operating conconnected to anode 12 and cathode 13, re-

spectively. The physical dimensions 0 elements in a thermionic tube change with temperature.

ftheof the tube brought ated vessel, a multiplicity of ature. The frequency characteristics of the control electrode circuit may be counteracted as well as the changes in the frequency characteristics of the anode circuit. An increase in the physical dimensions of the elements increases the capacity and hence decreases the frequency of the generated energy. will be seen, condenser 9l0, is connected in parallel with the capacity of the anode-cathode elements, Bi-metallic member 8 is mounted with respect to its directionof expansion in such a manner as to decrease the capacity of condenser 9-10 when the capacity of the anode-cathode electrodes increases, Since these two capacities are in parallel, the internal capacity of the tube remains unchanged.

I realize that many modifications of my invention are possible in high frequency signaling systems. Radiating systems are subject to frequency variation because of temperature changes, coupling circuits become non-resonant because of temperature changes and in ultra-high frequency work every part of a high frequency circuit is affected by temperature variation.

I desire that bodiments of my invention are in no way to be restricted by the foregoing specification or by the accompanying drawing but only by the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States is as follows: I

1. A thermionic tube comp electrodes therein, a compensating condenser com rising a pair of plate members, one of said p ate members being connected with one of said electrodes, and a thermoexpansive element supporting the other of said plate members with respect to said first mentioned said thermoexpansive element being connected with another of the electrodes within said tube for the conductive transfer of heat therefrom for controlling the'spacial relation of said plate members accordin to the variation in t mperatures within said tube. 2. A thermionic tube comprising an evacm- In testimony whereof aflix my CHESTER L. DAVIS.

it be understood that the emrising an evacuplate member, 

